Digital video cameras are increasingly spreading among the masses. Many of the latest mobile phones are equipped with video cameras offering users the capabilities to shoot video clips and send them over wireless networks.
Digital video sequences are very large in file size. Even a short video sequence is composed of tens of images. As a result video is always saved and/or transferred in compressed form. There are several video-coding techniques, which can be used for this purpose. MPEG-4 and H.263 are the most widely used standard compression formats suitable for wireless cellular environments.
To allow users to generate quality video at their terminals, it is imperative to provide video editing capabilities to electronic devices, such as mobile phones, communicators and PDAs, that are equipped with a video camera. Video editing is the process of modifying available video sequences into a new video sequence. Video editing tools enable users to apply a set of effects on their video clips aiming to produce a functionally and aesthetically better representation of their video. To apply video editing effects on video sequences, several commercial products exist. However, these software products are targeted mainly for the PC platform.
Since processing power, storage and memory constraints are not an issue in the PC platform these days, the techniques utilized in such video-editing products operate on video sequences mostly in their raw formats in the spatial domain. In other words, the compressed video is first decoded, the editing effects are then introduced in the spatial domain, and finally the video is encoded again. This is known as spatial domain video editing operation.
The above scheme cannot be applied on devices, such as mobile phones, with low resources in processing power, storage space, available memory and battery power. Decoding a video sequence and re-encoding it are costly operations that take a long time and consume a lot of battery power.
In prior art, video effects are performed in the spatial domain. More specifically, the video clip is first decompressed and then the video special effects are performed. Finally, the resulting image sequences are re-encoded. FIG. 1 illustrates the general procedure in conventional video editing. The major disadvantage of this approach is that it is significantly computationally intensive, especially the encoding part. Such a system is unsuitable for a mobile platform. Because of the requirements in spatial domain operations, video editing systems on mobile devices are rarely used, and the available editing features are also very limited.
It is thus advantageous and desirable to provide a method of video editing without the disadvantages of the prior art process.